Harold s



H. s. OSBORNE. COMPOSITE SIGNALING CIRCUITS.

APPLICATION FILED JUNE 8. I91].

1 ,3 1 4,828. Patented Sept. 2, 1919.

//V V E IV TOR I Harddd (22120326 ,4 TTORNE) 25 telephone repeater station. -The telephone UNITED STATES PATENT OFFICE,

' HAROLD S. OSBORNE, OF NEW YORK, N. Y., ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

COMPOSITESIGNALING-CIRCUITS.

Specification of Letters Patent. Patented Sept. 2, 1919.

Application filed June 8, 1917. Serial No. 173,527.

To all whom iz may concern:

Be it known that I, .HAROLD S. OSBORNE,

' residing at New York, in the county of New York and State of New York, have invented certain Improvements 1n Composite Signal- ,ing-Circuits, of which the following is a posited telephone and signaling lines. Its

object is to protect the telephone repeater from the signaling currents, and to provide -n1eans for conducting the signaling current around the telephone repeatler statlon w th- ,out impairing the impedance balance necessar v for repeater operati n.

' eren'ce to the accompanying drawing which The invention is best understood by refis a diagram of a two-way, two-repeater system embodying the arrangements of my invention.

said inferior limit.

Referring to the accompanylng drawing a telephone and telegraph transmission line is divided into two sections 1 and 1' at a repeater is of the well-known two-way tworepeater type and comprises two similar and equal parts R and R. Line section 1 is connected at terminals 3 and 4 to an electric wave filter 5. Said wave filter is a connecting or artificial line comprising a plurality of sections, each section having a condenser 6 in series with each side of the line and two serially conne ted inductances 7, 7 in shunt across the lin the common terminals of eachv pair of ,serially connected inductances being connected to ground by conductor 8. The properties of the wave .filter are fully described in U. S. Patent 1,227,113 of May 22 1917, to

G. A; Campbell, wherein it is shown that a filter consisting of serial capacity and shunt inductance, transmits with negligible attenuation all currents of frequency above a preassigned inferior limit while attenuating and substantially extinguishingall currents of frequency less than It will be observed that filter 5 consists of two similar halves sym metrically related to ground and for the reason I'have termed I filter. The function of filter 5 is two-fold. First, it prevents low frequency signaling currents from entering the repeater apparatus while at the same time freely transmit line 22 to coil 21.

said filter a duplex metallic telephone clrcuit but as the con ground-return ting therelativoly high frequency telephonic currents. Secondly, by virtue of its duplex structure and grpund connectious, it prevents the flow of signaling current from one side of .the line to the other, and thus largely eliminates interference between'composited signaling sets associated with the same telephone circuit.

Filter 5 is connected through transformer t) to repeater circuit 10, said circuit comprislng two serially connected similar and equal coils 11. 11 of a threecoil transformer 12,

a coil 13 of a two coil transformer 14, con-' nected from the common point of coils 11,

11 to the other side of the circuit, and a coil,

15 of a' transformer 16, similar and equal to transformer 9. Coil 17' of transformer 14- I is connected. to the receiving element of repeater l8 while coil 19 is serially connected to the output circuit or transmitting element of repeater 18.

For repeater operation, it is essential that the impedance connected to the terminals'ofi coil 20, consisting of filter -5 and line 1, shall be accurately balanced orsimulated by the impedance connected to the terminals-of coil 21 of transformer 16. To this end it is customary to provideanartificial line 22, which may be of any of a number of forms well known to the art, whose impedance closely simulates the impedance of line 1. Since, however, line 1 is connected to coil 20 by filter 5, my invention provides an equivalent filter 23 which connects artificial It will be evident that said arrangements provide for proper impedance balance of line 1 and filter 5 providing that artificial line 22 proper balances line 1, and that the circuits are symmetrical withrespect to circuit 10. While I have illustrated filter 23 as of the duplex type and having the common point of each pair of serially connected incluctances 24, 24 connected to ground by conductor 25, it is not essential that said filter be of the duplex typeor have a ground connection. In fact each pair of serially connected inductances 24 and 24 might be equally well replaced by a single inductance element whose inductance is equal to twice that of each 0011 24.

When lines 1 and 1' serve not only as a ductors of two composited telegraph circuits, means must be provlded for conducting the telegraph currents past the telephone repeater; that is, shunt the telegraph current from lines 1m 1 and from line 1' to line 1. This may be 'done in accordance with this'invention by connecting terminals 3 and 3' by 'a conductor 26 contain ing one or more retardation coils 27, 27 and similarly connecting terminals 4 and 4 by a conductor 28 containing one or .more -reeffect maybe eliminated in accordance with this invention, however, by connecting terminals 30 and 30. of artificial lines 22 and 22 through one or more retardation coils 31v and 31 similar and equal'to coils, 27-, and

likewise connecting terminals 32 and 32 through one or more retardation coils 33 and 33, similar and equal to coils 29,':so that the effect on the repeater of currents flowing through coils 27 and 29-is counteracted by the effect of equal and opposite currents flowing throughroils 31 and 33.

' It will thus be seen that this invention may be applied in any case where it is desired to prevent the tendency oftelephone repeaters 'to sing because of a mutual action between theincoming and outgoing lines, whether due to terminal apparatus of anysort, or'to the proximity of'the lines-themselves. In other words the tendency to sing may be counteracted bycreating between the two 1 artificial lines a mutual action equivalentto that between the line sections themselves.

Whatis claimed is: v 1-. In a'two-way two-repeater system, two

' transmission line sections, two artificial lines individually associated with said line sections, 'a'broad band wave filter connecting each line section with the repeater apparatus and two similar wave filters similarly connecting said artificial lines with said .re

peater apparatus.

2. In a two-Way two-repeater two-repeater station dividing said line into two sections, two artificial lines individually associated with said line sections, apparatus in shunt with said repeater station connect ing said line. sections, and apparatus asso' ciated with said artificial lines for duplicating therein the efi'ect of the shunt apparatus on the lines.

3. In a two-way two-repeater system, two transmission line sections,' a re eater interconnecting said lines,,two artifi ia'l lines associatedwith said-repeatenand said line sections, means for causing an interaction between said line sections, and means-for. pro ducing an equivalent interaction between the artificial lines.

.4. A composite transmission system, comprisin metallic telephone line sections, each side oi said line sections being used as a tele graph ClI'Cllll}, a repeater interconnecting said section's, conductive paths extending from each side of one of said line sections to corresponding sides of another line section and ,in shunt with said repeater, means in said paths to permit the transmission of telegraph currents but substantially preventing the transmission of telephone currents, balancing net works associated with said repeater for balancing each line section. and

conductive paths between said balancing net worksfor simulating the electrical characteristics of said first mentionedpaths.

#In testimony whereof, I have signed my name to this specification 1n the presence of two subscribing witnesses, this 19th day of May, 1917. a

' HAROLD S. OSBORXE.

Witnesses: V

CHESTER lVALLAon,

-A LFRED KAUFMANN .518 system, a. composited transmission line, a two way 

